Are parasitoids serving as the conduit for the spread of endosymbionts?
Parasitoids can serve as a driving force for the horizontal transfer of endosymbionts (Haine, Pickup, & Cook, 2005) as their lifestyle entails close cellular and tissue contact with their host. Horizontal transfer involving parasitoids is generally unidirectional (from host to parasitoid) because they usually end up killing the host. But parasitoids can also act as phoretic vectors (Ahmed et al., 2015; Gehrer & Vorburger, 2012) and can transmit Wolbachia by sequential probing of infected and uninfected hosts. Moreover, horizontal transfers can also happen between parasitoids if infected and uninfected larval parasitoids share the same host (Huigens, De Almeida, Boons, Luck, & Stouthamer, 2004). Such habits can also facilitate multiple infections if parasitoids infecting same host have different endosymbiont infections. As these multiple infections come in close contact, they can undergo recombination. Such parasitoid-mediated horizontal transfer could be an explanation for the distribution of A supergroupWolbachia infections in our sampling. Out of the 17Wolbachia A supergroup STs found, nine STs were found in morphospecies which are parasitoid wasps (Hymenoptera). Seven STs were found from Platygastridae and one each from Bethylidae and Diapriidae (Table 1). Therefore, the comparatively higher incidence of recombination in Wolbachia supergroup A infections could be due to their presence in parasitoid hosts (Mascarenhas et al., 2016). Similarly, predators and parasites can also be conduits for the spread of endosymbionts as speculated by predation of infectedArmadillidium vulgare by uninfected Porcellio dilatatus(Le Clec’h et al., 2013) and predatory mite Metaseiulus occidentalis and its prey, Tetranychus urticae (Hoy & Jeyaprakash, 2005). In soil arthropod community, we also observed incidences of Wolbachia recombination amongst predators.Wolbachia F supergroup ST-552, infecting morph0148 (Araneae-Zelotes ), had a fragment of gatB gene similar to A supergroup ST-544 infecting morph0076 (Araneae- Orthobula ). Also,fbpA gene of ST-544 was found to have probably recombined with ST-570 infecting Morph0375 (Coleoptera- Monolepta sp. ). Apart from such trophic interactions within the community, if any member of a community interacts with individuals of other community then it is likely to spread endosymbionts from one community to other.